No, because I can also communicate in real time over IM.

Additionally the social protocols are different. An email requires (some level of) planning and completeness. An IM can include just one question without reams of context, or it can involve a long detailed back-and-forth.

Questions over IM can be resolved in minutes or hours. Questions over email somehow morph into hideous monstrosities that waste days without anyone being satisfied with the answers.

And of course your mileage may vary, different organizations are different, etc...